To hold sufficient strength and to reduce cost by drawing a flat plate- like steel plate provided with a center projecting part and a tread part, cutting the drawn steel plate into the length of the outer periphery of a rim, forming it into a ring shape by a roll bending means, and welding both ends.

A flat plate-like steel plate provided with a center projecting part 12 and a tread part 13 is formed by a roll bending means, the drawn steel plate is cut into the specified length and formed into a ring shape by a roll bending means. Therefore, a rim 8 can be manufactured at low cost. The total length of the central projecting part 12 in the longitudinal direction of the drawn steel pipe is set larger than the total length of the tread part 13 when the flat plate-like drawn steel pipe is cut into the prescribed length, and both end surfaces in the longitudinal direction are formed on a groove inclined surface for welding. Therefore, the facing bottom parts on both ends of the central projecting part 12 and the tread part 13 can be brought into contact with each other in roll bending, and welding can be reliably and easily performed in relation to the part of the groove.